The present invention relates to a process and station for changing product in an installation for spraying coating product.
It is known, for example from EP-A-0 274 322, to use a reservoir, mounted at the end of an arm of a multi-axis robot, for supplying coating product to a spray supported by this arm, in particular in the case of an installation for spraying an electrically conducting coating product by means of a spray of an electrostatic type. This state of the art provides using a fixed spray on the arm of the robot and cleaning it and filling it with new coating product as a function of needs. According to a variant, the reservoir is removably mounted on the spray and a plurality of reservoirs are used as a function of the coating product chosen. Finally, according to a second variant, two reservoirs are used alternately.
In all cases, it is necessary to clean the spray, which is permanently mounted on the robot arm, and to prime it with new coating product. These rinsing and priming operations are relatively long while the time allocated to changing coating product tends to decrease. In effect, in the case of an automobile production line, the tendency is to increase production rates and therefore the speeds of advance of the conveyor belts, the change of coating product being effected in a time corresponding to the space separating two consecutive vehicle bodies, the available time being all the shorter as the speed of conveyance increases.
It is an object of the present invention to solve these problems by proposing a novel process and a novel station for changing coating product, which allow a rapid change while the quality of the cleaning effected remains optimum.
The above and other objects are achieved, according to the present invention, by a process for changing product in an installation for spraying coating product, comprising at least one robot, adapted to move a first sprayer and a first reservoir associated therewith opposite objects to be coated, this process comprising a step of bringing this reservoir towards a suitable area of a cleaning/filling station, characterized in that it consists in:
separating a sub-assembly, comprising the first reservoir and the first sprayer, with respect to the robot;
connecting with this robot a second, similar sub-assembly comprising a second reservoir and a second sprayer, this second sub-assembly being adapted to be used for spraying coating product during cleaning and/or filling of the first reservoir and the first sprayer, and
proceeding with cleaning and/or filling of the first reservoir and the first sprayer in said area.
Thanks to the invention, the first reservoir can be cleaned and filled with new coating product in masked time. The spray is also cleaned and primed with the new coating product in masked time, with the result that the only steps of the cleaning/filling process which must be taken into account in the calculation of the time taken to change the product, are the steps of separation of the first sub-assembly from and of connection of the second sub-assembly on the arm of the robot. In other words, the time which was consumed up to the present time for cleaning the spray and priming it with new coating product is now available for spraying by means of the second sub-assembly, since these operations take place on the first sub-assembly in masked time while the second sub-assembly is being used.
According to a first advantageous aspect of the invention, the process consists in supplying the first sub-assembly with air, cleaning product and/or coating product in the suitable area of the cleaning/filling stations, before it is separated from the robot. In this way, certain functions of the spray and/or of the reservoir may be maintained, including during separation between this sub-assembly and the robot.
According to another advantageous aspect of the invention, the sub-assembly is supplied with air, electric current, cleaning product and/or coating product by means of two mobile units, a first unit being connected to the sub-assembly before its separation from the robot, while a second unit is connected to the sub-assembly after its separation from the robot, in place of the connection part of the robot.
In particular, the spray, or sprayer, may be supplied with air continuously to form a bearing between parts of the spray, or sprayer, that are in relative movement. This proves particularly advantageous in the case of a rotary sprayer, as the continuous supply of air to the bearing avoids any risk of this bearing locking or seizing.
The invention also relates to a product changing station in an installation for spraying coating product, which carries out the process as described hereinbefore. This station, which comprises at least two reservoir cleaning/filling areas, is characterized in that these areas are adapted each to receive a sub-assembly formed by a reservoir and a spray while this sub-assembly is disconnected from the robot, means being provided for cleaning and/or filling the reservoir and the spray in each of these areas.
In this way, each sub-assembly may be cleaned and/or filled in masked time while a similar sub-assembly is being used on the robot.
According to a first advantageous aspect of the invention, the reservoir and spray cleaning/filling means comprise two mobile units adapted to be coupled independently in two areas of connection of the sub-assembly, a first unit being adapted to be connected to the sub-assembly mounted on the robot while the second unit is adapted to be connected to the sub-assembly in place of the connection part of the robot. The first unit advantageously comprises means for connection between a source of compressed air and a bearing formed in the spray, between two parts in relative movement. In this way, the bearing may be permanently supplied, which avoids the risks of this bearing locking or seizing.
In particular, the second unit may comprise a jack whose rod is adapted to manoeuvre a piston of the reservoir, in particular for bleeding this reservoir.
According to another advantageous aspect, the station comprises means for locking a sub-assembly in each of the cleaning/filling areas, by rotation of a ring surrounding this sub-assembly, and adapted to cooperate with projections on this sub-assembly in order to rotate it with respect to the robot. Displacement of this ring between a position of locking and a position of unlocking of the sub-assembly, is advantageously controlled by a jack.